Effects of lysine to metabolizable energy ratio in the diet on growth performance and carcass characteristics of growing pigs

Abstract

To evaluate the effects of dietary digestible lysine and metabolizable energy ratio (Lys:ME; g/Mcal) on growth performance and carcass characteristics of growing pigs, 70 crossbred barrows (Yorkshire × Landrace) were randomly allotted in a design of two complete blocks with five diets and seven replications of two pigs each. Pigs were fed ad libitum in two phases with diets containing 2.00, 2.29, 2.57, 2.85 and 3.14 g/Mcal in phase I (26.61-56.68 kg live weight) and 1.54, 1.77, 2.00, 2.22 and 2.45 g/Mcal in phase II (56.68-83.36 kg). Average daily feed intake (ADFI), average daily gain (ADG) and feed:gain ratio (FG) were evaluated. Backfat depth (BF) and longissimus muscle area (LMA) were measured and lean gain (LG) and lean yield (LY) were calculated. In the evaluated phases, ADG, ADFI and FG did not significantly differ among treatments. In Phase II, ADG increased and FG decreased linearly (P <0.05) with the ratio Lys:ME. In Phase I, the ratio affected (linear, P <0.05) BF. The greatest BF (4.67 mm) corresponded to 2.00 g/Mcal. The LG showed a quadratic (P <0.05) and linear (P = 0.01) response in Phases I and II, respectively, reaching 398 g/d with 2.85 g Lys/Mcal in Phase I. The ratio of Lys:EM within the range studied did not affect growth performance and the majority of carcass characteristics of growing pigs.